Everything You Need to Know about Narcissists, Psychopaths, and Abuse - click on this link: http://www.narcissistic-abuse.com/faq1.html
He abruptly loses interest in sex and in all his sexual partners. The frequency of his sexual activities deteriorates from a few times a day â to a few times a year. He reverts to intellectual pursuits, sports, politics, voluntary activities â anything but sex (a process that Freud labelled âsublimation.â) This kind of narcissist is afraid of encounters with the opposite sex and is even more afraid of emotional involvement or commitment that he fancies himself prone to develop following a sexual encounter. In general, such a narcissist withdraws not only sexually â but also emotionally. If married â he loses all overt interest in his spouse, sexual or otherwise. He confines himself to his world and makes sure that he is sufficiently busy to preclude any interaction with his nearest (and supposedly dearest). He becomes completely immersed in "big projects", lifelong plans, a vision, or a cause â all very rewarding narcissistically and all very demanding and time consuming. In such circumstances, sex inevitably becomes an obligation, or a maintenance chore reluctantly undertaken to preserve his sources of supply (his family or household). The cerebral narcissist does not enjoy sex and by far prefers masturbation or "objective", emotionless sex, like going to prostitutes. Actually, he uses his mate or spouse as an "alibi", a shield against the attentions of other women, an insurance policy which preserves his virile image while making it socially and morally commendable for him to avoid any intimate or sexual contact with others.
(From the book "Malignant Self-love: Narcissism Revisited" by Sam Vaknin - Click on this link to purchase the print book, or 16 e-books, or 3 DVDs with 16 hours of video lectures on narcissists, psychopaths, and abuse in relationships: http://www.narcissistic-abuse.com/thebook.html)